This present invention relates generally to temperature detection circuits, and more particularly to a low supply voltage and low power consumption temperature detector.
Thermal performance has become an increasingly important characteristic of integrated circuits (ICs). For one, such circuits behave differently at different temperatures. For example, as the temperature of a circuit changes, the electrical characteristics of the circuit also change, such as threshold voltage level, electron mobility, wiring/contact resistance, etc. Also, internally generated voltages used by various subsystems in an IC are sensitive to temperature changes such that performance of those systems can be compromised unless there is some way to compensate for the temperature variation. An accurate temperature detector is thus necessary to determine when a circuit is operating outside of predetermined normal operating conditions. Methods then can be initiated to compensate for high or low temperatures, that is, temperatures outside of the predetermined normal operating temperatures.
For example, if a circuit is too hot, the system frequency may be reduced in order to decrease the circuit temperature. Conversely, if the temperature is low, the system frequency may be increased in order to improve performance. Additionally, some circuits or components may need to be shut-down when the temperature exceeds a predetermined threshold level, and in some applications, such as memories, there are instances where secret information should be erased before the memory fails due to operating at very low or high temperatures.
Further, many electronic devices, such as portable computers, cell phones, hand-held game devices and personal digital assistants, are sensitive to power consumption. That is, low power consumption is desirable in order to preserve battery power. Thus, a temperature detector circuit should consume as little power as possible.
Also, as the feature sizes of ICs are reduced, the supply voltage used by these circuits decreases. For example, a 0.7 μm CMOS device operates at around 5V, while a 0.18 μm CMOS device operates at around 1.8V or lower. Such lower operating voltages make the design of temperature sensors more challenging because at lower operating voltages the characteristics of semiconductor devices become more inconsistent. Thus, there is a need for a temperature sensor that can operate at very low voltage and consume little power.